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In this research, aluminum-based drinking water treatment sludge is used as a starting material and immobilized by sodium alginate to develop low cost adsorbent for the removal of methylene blue (MB) from aqueous solutions. The studied variables included pH, adsorbent dose, initial MB concentration and contact time. Characteristics of the adsorbent were also studied using scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR). It was revealed from kinetic tests that removal efficiency of MB was 88.5% under the optimum conditions of pH 8, initial MB concentration of 50 mg/L, contact time of 60 min, and adsorbent dose of 0.3 g/L. The oxygen functional groups such as -OH, C-O-C and C=O were found on the surface of developed adsorbent by FTIR. In addition, the adsorption data fitted well the Langmuir adsorption model with the maximum sorption capacity of 909.1 mg/g, and followed the pseudo-second-order kinetics. Findings of this study indicate that the prepared adsorbent is promising for further development of an effective and economical adsorbent material in the near future. [ABSTRACT FROM AUTHOR]

In the present study, we have used a simple and cost-effective removal technique by a commercially available Fe-Al-SiO2 containing complex material (hardened paste of Portland cement (HPPC)). The adsorbing performance of HPPC and modified HPPC with perlite for removal of cefixime from aqueous solutions was investigated comparatively by using batch adsorption studies. HPPC has been selected because of the main advantages such as high efficiency, simple separation of sludge, low-cost and abundant availability. A Taguchi orthogonal array experimental design with an OA16(45) matrix was employed to optimize the affecting factors of adsorbate concentration, adsorbent dosage, type of adsorbent, contact time and pH. On the basis of equilibrium adsorption data, Langmuir, Freundlich and Temkin adsorption isotherm models were also confirmed. The results showed that HPPC and modified HPPC were both efficient adsorbents for cefixime removal. [ABSTRACT FROM AUTHOR]

The adsorption of methyl orange dye from aqueous solution onto penta-bismuth hepta-oxide nitrate, Bi5O7NO3, synthesized by precipitation method, was studied in a batch adsorption system. The effects of operation parameters such as adsorbent dose, initial dye concentration, pH and temperature were investigated. The adsorption equilibrium and mechanism of adsorption was evaluated by Langmuir and Freundlich isotherm and different kinetic models, respectively. The results indicate that adsorption is highly dependent on all operation parameters. At optimum conditions, the adsorption capacity was found to be 18.9 mg/g. The adsorption data fits well with the Langmuir isotherm model indicating monolayer coverage of adsorbate molecules on the surface of Bi5O7NO3. The kinetic studies show that the adsorption process is a second-order kinetic reaction. Although intra-particle diffusion limits the rate of adsorption, the multi-linearity plot of intra-particle model shows the importance of both film and intra-particle diffusion as the rate-limiting steps of the dye removal. Thermodynamic parameters show that the adsorption process is endothermic, spontaneous and favourable at high temperature. [ABSTRACT FROM AUTHOR]